Seamless hollow article and process of making same



Patented June 29, 1926.

UNITED s'ryras v 1,590,271 PATENT OFFICE.

IBEDEBIK M. BECKET, OF NEW YOBK, Y ASSIGNOR TO ELECTED METALLURGICAL (10., A CORPORATION OF WEST VIRGINIA.-

snmnss narrow aa'rrcm AND. rnocnss or MAKING sans.

Io Drawing.

This invention relates primarily to the manufacture of seamless tubing or other hollow articles from allo s of the general type known as chrome-irons, which are 6 characterized by their greatresistance to corrosion particularly by their resistance to oxidation at high temperatures.

Is has heretofore been possible to make tubing of chrome-iron alloys by the process 10. of cutting rolled sheets into strips, forming these cylinders and subsequently welding them by means of gas or electricity to form a tube. This method is entirely practicable and results in a product which is satisfactory for many purposes; however,

for many purposes, especially where a thick walled tube-is required there are certain disadvantages inherent in the welded tubes. 'Among these are difliculties in welding '20 heavy walls, danger of porous spots in the welds and rather large unit-cost. A seamless tube possesses the further advantages of being more substantial or strong mechani-- cally and not liable-to open up as a result of repeated expansion strains due to alternate heating and cooling.

Under these conditions it is natural that many efiorts should have been made in the pastto make seamless tubing from various compositions of iron-chromium alloys, using the methods which have proven successful in themanfacture of seamless tubing from steel. Many such attempts have been made, but inno case, so far as I am aware, have they been successful; and it is the present general opinion among metallurgists that there is little prospect'of anindustrial' solution of I the problem.

:- 'It is well known a those skilled in the manufacture of seamless tubingfrom steel bly the Mannesmann orsimilarprocess that .te

piercing of the billet not only forms the initlal'li'ole but tears the walls of it to .a

greater or less extent; but that in the subsequent hot working, the rolling and pressing movements autogenously weld the tears to produced-and in this way effectively heal 7 these ruptures. Knowing that chrome-irons once torn will 'not re-weld even under the most favorable conditions of :temperature and pressure which have. yet been brought to bear upon them, is has naturally been concluded by those skilled in this art that V the manufacture of seamless tubing fromv chrome-iron, and especlally from 1ron-chro-.

strength of a variety of chrome-irons, in-

"Application filed October 15, 1925. Serial No. 62,658.

mium alloys relatively high .in chromium, containing, say, upward of about 10% of chromium would be impossible by any methods now available. The extreme hardness and toughness of chrome-iron alloys at high tem eratures,;such as are normally used in siml ar operations upon steel, has strongly confirmed this opinion. I

Nevertheless, in determining the tensile eluding those of chromium contents both above and below 20% of chmorium-. I have observed a great and unexpected ductility inthese alloys within the range of temperature lying approximately between 1000 and 1175 C.; and my. experimentation has shown that many of the .mostuseful chrome-- irons moderately low in carbon can be successfully pierced from billets and rolled to seamless tubes through the emplo ment of appropriatemodifications of stan arcl processes and-by the use of existing machinery and pre-heating equipment. Taking advantage of the above observation I have successfully pierced billets of various hrome-irons and have rolled the pierced billets to seamless tubes of standard dimensions and mer'chantable lengths. For example, I-have found it commercially practicable to pierce and roll to excellent seamless tubing iron-chromium alloysof'the following approximate compositions, the balance in each case being chiefly iron:

Cr. 26.89 C 0.25- 0.18 on Si. 0144. I t 0.37 Mn. 0.53 v I 0.96 P. 0.018 Not determined.

s 0.02 Do 5 Ni 0.542 Do to allow of t eir being converted into seam- "9-" content materially higher than 0.25%. Maximum limits of chromium and carbon,-

or of alloying elements, cannot however be Stated, as these will of course depend upon the strength of piercing points, and the strength and power capacity of the pierc- 9 ing machinery available for the work. It

is of course recognized that there must exist an upper limit of carbon content at which an alloy of any particular chromium content will lose that measure of ductility which is essential to the success of the operation.

Seamless steel tubing is made 'by piercing billets of low carbon steel by the Mannesmann, 'Steifel or similar process and subse uently-rolling to the desiredcalibre and thickness of wall. The steelbillet is pierced preferably within the range of 1250 to 1350 0.; and even higher temperatures are hazarded in order to secure greater softness 5 and a, consequent increase in the speed of piercing. The upper limit of temperature is indicated by the appearance ofincipient red-shortness. In heating steel billets preparatory to piercing, and particularly through the higher temperatures of the preheating ranges, the furnace atmosphere must be maintained in a reducing condition in order. to avoid superficial oxidation of the steel, a condition unfavorable to the quality and appearance of the finished tube.

In contradistinction to the above conditions, which govern the making of steel tubing,the temperatures which I have found "best adapted for the piercing of billets of the various chromeirons,-and especially those having chromium contents of 20% andupward,+lie below about1175 C. and in most .cases .at least within the range S10,0 O: "-11 75-C. I At -temperatures substantially below 1000 Gqpiercing of the.'commercial varieties of .chromejiron becomes difiicult; and above about 1200 C. they develop red-shortness. 4. 1 In-heating the billets preparatory .to piercing,.the furnace need not present a reducing atmosphere, as in the caseof steel billets,

since the resistance of the commercial vari eties offchrome-iron to oxidation at h gh '1 temperatures establishes a wide tolerance of oxidizing conditions. On the other hand in the upper part of the pro-heating range,

and notably above 1OU0 0., prolonged exposure to a highly reducin furnace atmosphere will embrittle these alloys.

In heating billets of the chrome-irons'the rate of rise in temperature, especially up to about 600 (3., is preferably uite slow as compared with that permissi 1e and "employed' in heating billets of steel, in order to avoid any tendency to cracking the chrome-iron. After reaching red-heat, the subsequent rise in temperature can well proceed as rapidly as is now usual in heating steel for billet-piercin But before piercing I have found it desirable to hold the billet of chrome-iron at the piercing temperature until'all parts of it have reached approximately the same temperature, in

order that the deformation of the alloy and- "1050 and 1150 C. This is commonly accomplished in about 3 hours, and the billets are usually held at the piercing tempera-' ture for anadditional hour or more in order to e ualize the temperatures of all the billets of t e batch, as well as to secure a uniform temperature throughout the material of each billet. Each billet is then ierced, and rolled into seamless tubing 0 the desired dimensions a For the manufacture of seamless tubing by hot piercing and rolling, chrome-iron alloys should be produced, poured, cast and rolled under conditions which will provide billets free of slag, oxides and other nonmetallic inclusions. They should also contain the. minimum of dissolved oxides or other impurities eitherdissolved or chemically combined, which can contribute to embrittling the billet at the temperatures used for piercing or in the. subsequent rolling. I have found that inclusions as well as impurities dissolved or otherwise contained in chrome-irons may render them unsuitable or even useless as material forhotpiercingand subsequent rolling to seamlesstubes. v

I have found that seamless tubes of chrome-iron can also be made by hot-pierc ing. a cylindrical billet to form a cup, cropplng the cup to an open cylinder, and rolling the latter into tubingof the re uired di- ,mensions. i I have also made hotrawn or hot-pressed pots or containers of chromeiron by means of standard machinery come men] used for the drawing or pressing of the similar vessels from steel, by an application of the methods above described m connection with the operation of making seamless tubing. Hence I employ theterm seamless tubing. herein in its broad significance, as including seamlesshollow articles of various kinds.

The range of usefulnessmnd the variety of appropriate applications of seamless'tubing made of chrome-iron are obvious. Tubing produced from these alloys may prove almost indispensable as an element of construction in .furnaces, recuperato-rs, superheaters, autoclaves and stills, and inmany other forms of equipment and apparatus which encounter hightemperatures as 'well as erosive and corrosive agencies. For all such applications chrome-iromtubing offers the ease of fabrication and high thermal conductivity common to most metals and alloys, and in addition presents a combinationofstrength and resistance to oxidation at high ,temperatures, as well as resistance to many forms of corrosion, which are not simultaneously foundin any other metal or alloy.

I claim: y 1. Process of *makin a seamless hollow article by hot piercing ollowed by working such as rolling yor .drawing, comprising piercmg an iron-chromlum alloy containlng atleast about10% of chromium at a temperature lying approximately between 1000 and 1175 C.

2. Process of making a seamless hollow article byhotpiercing followed by Working such as rolling or drawing, comprising piercing an iron-chromium alloy containing at least 20% chromium, ata temperature lying approximately between 1000 and 1175 C,

3. Process of making a seamless hollow article by hot piercing followed by workiug'such'as rolling or drawing, comprising piercmg approxlmately 25% chromium, at a temperature lying approximately between 1000? and 1175C.

4. A hollow article of the character de-' scribed having seamless walls of an ironchromium alloy containin'g 'a t least 10% chromium produced by aIhot-piercing operation.

5'. A hollow article of the character described having seamless walls of an ironchromium alloly containing at least 20% an iron-chromium alloy containing chromium produced by a ho -piercing operation.

. 6. A hollow article ofthecharacter de scribed having seamless walls of an iron- I chromium alloy containing approximately 25% chromium produced by a hot-piercing operatiom ture. FREDERICK M. BECKET.

In testimony whereof, I afiix my signa- 

